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| United States Patent |
5,210,356
|
|
Shamshoum
, et al.
|
May 11, 1993
|
Toluene disproportionation employing modified omega zeolite catalyst
Abstract
The present invention relates to a stable, highly active and selective
modified omega zeolite, and its preparation and use in toluene
disproportionation.
| Inventors:
|
Shamshoum; Edwar S. (Houston, TX);
Ghosh; Ashim K. (Houston, TX);
Schuler; Thomas R. (Galena Park, TX)
|
| Assignee:
|
Fina Technology, Inc. (Dallas, TX)
|
| Appl. No.:
|
808126 |
| Filed:
|
December 16, 1991 |
| Current U.S. Class: |
585/475; 585/467 |
| Intern'l Class: |
C07C 005/52 |
| Field of Search: |
585/467,475
|
References Cited
U.S. Patent Documents
| 4241036 | Dec., 1980 | Flanigen et al. | 423/328.
|
| 4245130 | Jan., 1981 | Jones et al. | 585/481.
|
| 4724067 | Feb., 1988 | Raatz et al. | 208/120.
|
| 5030432 | Jul., 1991 | Occelli | 423/328.
|
Primary Examiner: Pal; Asok
Assistant Examiner: Achutamurthy; P.
Attorney, Agent or Firm: Cheairs; M. Norwood, Caddell; Michael J., Ellsworth; Betty M.
Claims
We claim:
1. In a transalkylation process for the disproportionation of a toluene
containing feedstock over a steam modified and metal-promoted omega
zeolite catalyst to produce benzene and xylene(s), the steps comprising:
(a) passing a cofeed of hydrogen gas and substantially pure toluene into a
reaction zone and contacting it with a steam-modified and nickel-loaded
omega zeolite catalyst, the catalyst having a silica to alumina molar
ratio in the range of about 25:1 to 150:1, the feedstock being supplied to
the reaction zone at a rate sufficient to provide a toluene LHSV of about
2;
(b) conducting the disporportionation reaction within the reaction zone at
a temperature within the range of about 250.degree.-480.degree. C. and at
a pressure of at least 600 psig; and
(c) withdrawing the disproportionation product containing benzene and
xylene(s) from the reaction zone.
2. The process according to claim 1 wherein the reaction zone is operated
at a temperature of about 250.degree.-320.degree. C.
3. The process according to claim 1 wherein the reaction zone is operated
at a temperature of about 280.degree. C.
4. The process according to claim 1, wherein the toluene conversion level
is greater than 46% and the conversion level is maintained by adjusting
the reactor temperature.
5. The process according to claim 1, wherein the toluene conversion level
is about 48% and the conversion level is maintained by adjusting the
reactor temperature.
6. The process according to claim 1, wherein the omega zeolite catalyst
preferably exhibits a silica to alumina molar ratio of about 30:1 to 50:1.
7. The process according to claim 1, wherein the omega zeolite catalyst
most preferably exhibits a silica to alumina molar ratio of about 35:1 to
40:1.
8. The process according to claim 1 wherein the metal-promoted omega
zeolite catalyst contains an amount of nickel within the range 0.3-0.8
weight percent.
9. The process according to claim 1 wherein the metal-promoted omega
zeolite catalyst contains an amount of nickel within the range 0.45-0.7
weight percent.
10. The process according to claim 1 wherein the metal-promoted omega
zeolite catalyst contains an amount of nickel which is about 0.6 weight
percent.
11. The process according to claim 1 wherein the hydrogen gas is cofed with
the toluene in a weight percentage concentration of about 3.5:1 to 4.5:1.
12. The process according to claim 1, wherein the level of (liquid)
non-aromatic by-product compounds in the disproportionation product
decreases sharply with time on stream and shows a stable value of less
than 1 wt. % of the disproportionation product.
13. The process according to claim 1, wherein the level of benzene product
comprises a stable weight percentage value of about 40-41% of the
disproportionation product.
14. The process according to claim 1, wherein the rate of catalytic
deactivation, as measured by change in reactor temperature per day in
order to maintain about 48% toluene conversion, is less than 1.degree. C.
per day.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the disproportionation of alkylaromatic
feedstreams and, more particularly, to the disproportionation of toluene
containing feedstocks employing a metal-promoted, steam-modified omega
zeolite catalyst.
2. Description of the Related Art
The disproportionation of toluene involves a well-known, catalyzed
transalkylation reaction in which toluene is converted to benzene and
xylene in accordance with the following reaction:
##STR1##
Reaction (1) is mildly exothermic. Crystalline aluminosilicates, or
zeolites, are well-known in the art and have found extensive application
as hydrocarbon catalysts. While many zeolites occur naturally, more than
40 species of synthetic crystalline zeolites are known to have been
prepared within the past decade. These synthetic compositions are
distinguishable from each other and from the naturally occurring zeolites
on the basis of factors such as composition, crystalline structure,
adsorption properties and, perhaps most importantly, characteristic x-ray
powder diffraction pattern. Zeolites are of an ordered crystalline
structure comprising "cages" or cavities occupied by large ions and water
molecules, both of which have considerable freedom of movement, permitting
ion exchange and reversible dehydration. Access to these cavities or
"channels" is gained by way of orifices within the crystalline lattice.
These openings limit the size and shape of molecules that can be adsorbed.
A separation of mixtures of molecules based upon molecular dimensions,
whereby certain molecules are adsorbed by the zeolite while the entry of
others is prevented, is therefore possible. It is this characteristic
property of many crystalline zeolites that has led to their designation as
"molecular sieves." For a general discussion of zeolite catalysts,
reference is made to Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd
Edition, 1981 under the heading "Molecular Sieves", Vol. 15, pages
638-643.
In addition to molecular size and shape, however, other factors may also
influence the selective adsorption of certain foreign molecules by
molecular sieves. Among these factors are: the polarizability and polarity
of the adsorbate molecules; the degree of unsaturation of organic
adsorbates; the size and polarizing power of the interstitial cation; the
presence of adsorbate molecules within the crystalline lattice
(interstitial spaces); and the degree of hydration of the zeolite.
In addition to the unique adsorption properties of zeolite molecular
sieves, certain of these materials, particularly when chemically modified,
are effective catalysts in hydrocarbon conversion processes such as
reforming, cracking, isomerization, dehydrogenation and the like. Because
the mechanisms involved in these catalytic applications are complex,
however, the precise chemical properties of the zeolites which contribute
to a particular catalytic activity are not fully understood.
As indicated, many catalytic applications have been discovered for certain
zeolites. Among the more widely used and studied zeolite forms are:
mordenite, beta and ZSM-5. Lesser known and studied omega zeolite, which
is the catalyst employed in the present invention, was first identified by
Flanigen, et. al. in U.S. Pat. No. 4,241,036. According to Flanigen, et.
al. omega zeolite is not only a distinct species of zeolite molecular
sieve but also is a member of a new structural class of zeolites
exhibiting a unique and previously unknown framework arrangment of
SiO.sub.2 and Al.sub.2 O.sub.3 tetrahedra. While Flanigen, et. al.
discloses only the composition of omega zeolite and various procedures by
which the composition can be prepared, the inventors did indicate that
various cation and decationized forms of zeolite omega could be effective
in the hydrocarbon conversion processes commonly referred to as cracking,
hydrocracking, isomerization, polymerization, hydrogenation, reforming and
paraffin alkylation. This indication notwithstanding, however, and as
compared to the aforereferenced and more widely used zeolites, the
catalytic properties of omega zeolite are considerably less well known or
studied. Low thermal stability has been the reason cited most frequently
for the dearth of investigative activity respecting omega zeolite.
According to extant scientific literature, omega zeolite may be destroyed
or may undergo a considerable decrease in crystallinity when calcined at
temperatures exceeding 600.degree. C. While a number of explanations have
been advanced, the reason for the thermal brittleness of omega zeolite
remains not well understood. Despite this uncertainty and the variety of
postulations, however, recent studies directed toward improving the
thermal stability of omega zeolite have been successfully conducted. For
example, in Volume 4 of the work entitled "The Synthesis and Thermal
Behaviour of Zeolite" (1984) pp. 263-269 by Araya, Abraham, et. al., it is
reported that the small quantity roasting of NaTMA omega form in an
apparatus of differential thermal analysis leads to a solid which remains
crystallized at temperatures up to 800.degree. C. This solid, however, is
not dealuminated and retains all initial alkali cations. Earlier work
involving the roasting of an NH.sub.4 TMA omega compound was reported by
Weeks, et. al., in an article appearing in the Journal of the Chemical
Society entitled "Thermochemical Properties of Ammonium Exchanged Type
Omega Zeolite," Farad Trans 1, 72(1976), 57. Despite some observed thermal
stabilization, however, the solid compound failed to demonstrate desirable
catalytic activity when tested in hydrocracking and isomerization
applications.
In addition to attempts to thermally stabilize the compound, the
dealumination of omega zeolite has also been the focus of some
investigative activity. U.S. Pat. No. 3,937,791 to Garwood, et. al.
discloses the dealumination of various zeolites, including omega zeolite,
by Cr (III) salts. This method leads to replacement of the aluminum atoms
by chromium atoms. Notwithstanding that the structure is dealuminated, its
chromium content is also fatally increased. U.S. Pat. No. 4,297,335 to
Lok, et. al. recommends a dealumination technique by treatment with
fluorine gas at high temperature. This treatment is applicable to various
zeolites but, when applied to omega, it results in degradation of the
crystalline structure. European Patent No. 100,544 to Gortsema, et. al.
discloses the dealumination of many zeolites, including the omega form, by
roasting in the presence of SiCl.sub.4 at temperatures lower than
200.degree. C., despite that higher temperatures are known to be required
for dealumination in accordance with such technique (Beyer, et. al.
Catalysis by Zeolites, (1980) p. 203). The dealumination of omega zeolite
by SiCl.sub.4 is in fact possible but only at temperatures, for example,
above 500.degree. C. as disclosed by J. Klinowski, et. al. JCS, Chem.
Commun. 1983, p. 525 and O. Terasaki, et. al. Proc. R. Soc. London (A),
395 (1808), 153-64). Treatment of the omega zeolite by this technique,
however, results in a virtually negligible increase in the SiO.sub.2 to
Al.sub.2 O.sub.3 ratio. Moreover, inasmuch as dealumination by treatment
with SiCl.sub.4 is applicable to omega zeolite it is essential to note
that this technique results in irremediable replacement of the aluminum
atoms of the structure with silicon atoms (H. Beyer, et. al. Catalysis by
Zeolites, B. Imelik, et. al. editors (1980), p. 203, Elsevier Amsterdam).
Despite the investigative activity described above, the most important
advance concerning efforts to both thermally stabilize and dealuminate the
omega zeolite form has apparently been made by Raatz, et. al. as disclosed
in U.S. Pat. No. 4,724,067. Therein, it is claimed that a practical and
useful hydrogen form of omega zeolite can be prepared by a process
involving alternating ion exchanges and acid etchings with thermal
treatments. Raatz, et. al. further disclose that their process yields a
thermally stable, dealuminated omega zeolite in hydrogen form which
functions as an active and selective catalyst in cracking and
hydrocracking reactions.
While it has been discussed that much investigative work has occurred
involving the use of zeolites as catalysts, it is clear that the use of
the omega form of the composition remains not fully understood. Moreover,
and perhaps due in some measure to the compound's reputation for thermal
instability, its known application in the field of alkylaromatic catalysis
has been limited to cracking and hydrocracking reactions.
In view of the foregoing, it is clear that a need in the art exists for a
means of employing omega zeolite in high level conversion of aromatic
hydrocarbons.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a method for
preparing a highly active, selective and stable metal-promoted and steam
modified omega zeolite catalyst for use in the disproportionation of
alkylaromatic feedstreams and, more specifically, in the
disproportionation of toluene containing feedstocks. The preferred
catalyst is of the type designated orthorhombic sodium alumino silicates
(zeolites) having a molecular weight in the range of about 2382 to 2886,
pore size of its main channel measuring about 7.4 Angstroms and a
SiO.sub.2 /Al.sub.2 O.sub.3 ratio from about 25:1 to 150:1. One
particularly advantageous parent catalyst was found to be a zeolite
catalyst denominated "Zeolite-Omega" which is sold by Universal Oil
Products Company of Des Plaines, Ill. (UOP).
The instant catalyst comprises a metal-promoted zeolite omega, preferably a
nickel/omega which characteristically contains about 0.3 to 0.9 wt. %
nickel and, preferably, about 0.6 wt. %. While nickel is the preferred
metallic hydrogenation agent, the modified omega zeolite catalyst may also
be loaded with other Group VIII metals such as Cobalt and Palladium.
The method by which the present zeolite is modified to form the catalyst of
the instant invention involves: subjecting the parent zeolite omega
composition to an initial ammonium ion exchange after which the resultant
dried powder is calcined to effectively remove the catalyst's organic
template; subjecting the calcined powder to two successive ammonium ion
exchanges; steaming the powder; subjecting the steamed powder to two
additional and successive proton ion exchanges under acidic conditions;
extruding the powder together with an established amount of alumina binder
followed by an additional calcination; and, finally, by employing standard
techniques, impregnating the solid extrudate with a desirable amount of a
metallic hydrogenation component.
In performing the process of the present invention, an alkylaromatic
feedstream, preferably pure toluene, is supplied to a reaction zone and
brought into contact with the molecular sieve transalkylation catalyst
comprising modified omega zeolite. The modified omega zeolite contains a
metallic hydrogenation component, preferably nickel, in a weight
percentage amount of about 0.3 to 0.9 and the final catalyst with 20%
binder is further characterized by a surface area of more than 420 m.sup.2
/gram. Hydrogen gas is also supplied to the reaction zone as a cofeed in a
molar ratio of about 3.5:1 to 4.5:1. The reaction zone is preferably
operated at a temperature of about 250.degree. to 480.degree. C. and at a
pressure of about 600 psig, thereby causing the disproportionation of the
alkylaromatic feedstock in the presence of the modified omega
zeolite/transalkylation catalyst. The resulting transalkylated aromatic
products are then recovered from the reaction zone.
A preferred application of the present invention involves the
transalkylation of toluene to produce benzene and xylene(s) in the
presence of the aforedescribed modified omega zeolite catalyst. The
process is performed at transalkylation conditions under which the
alkylaromatic feed material is at least 48% converted and relative
production of benzene equals or exceeds 40 weight percent.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 graphically illustrates the relationship between reactor temperature
and time on stream for each of the three metal loaded modified omega
zeolite catalyst samples studied.
FIG. 2 graphically depicts the product selectivity of the most preferred
metal loaded modified omega zeolite catalyst when employed in the
disproportionation of toluene and as a function of time on stream.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates to a stable, highly active and selective
modified omega zeolite, and its preparation and use in alkylaromatic
disproportionation. The preferred catalyst comprises a metal-promoted,
omega zeolite composition which is particularly useful in the
transalkylation of alkylaromatic compounds. The invention is particularly
applicable to the transalkylation of toluene under relatively low reaction
temperature producing desirably stable concentrations of benzene and
xylene(s) and near equilibrium conversion of the alkylaromatic starting
material. The metal-promoted omega zeolite of the present invention is
prepared by the modification of the crystalline omega zeolite as
synthesized. The basic procedure for the preparation of crystalline omega
zeolite, which is identified by its characteristic x-ray diffraction
pattern, is disclosed in U.S. Pat. No. 4,241,036 to Flanigen, et. al.
Additionally, other references such as U.S. Pat. No. 4,724,067 to Raatz,
et. al. and the earlier referenced JCS article by Weeks, et. al. discuss
crystalline omega zeolite compositions. The entire disclosures of each of
these references are incorporated herein by reference.
Prior to modification, crystallinity of the parent omega zeolite is
confirmed by way of x-ray diffraction analysis. Thereafter, the preferred
omega zeolite composition which exhibits a silica to alumina molar ratio
of 25:1 to 150:1 undergoes treatment as herein described.
Using standard techniques, the as synthesized zeolite omega composition is
initially subjected to an ion exchange medium such as an aqueous solution
of an inorganic ammonium salt, e.g. ammonium nitrate, in a relative
omega-zeolite-to-ammonium-nitrate weight percentage relationship in excess
of 1:2. Following this initial ion exchange, the omega zeolite is calcined
at a maximum temperature of about 570.degree. C. for a period of two or
more hours. This calcination procedure is designed to burn away the
organic template contained within the framework of the omega zeolite as
synthesized. After calcination, the omega zeolite is subjected to two
subsequent and successive ion exchange treatments each of which is
performed in the same manner as described above. Following the third ion
exchange, the omega zeolite is steamed, using standard techniques, at a
desirable temperature within the range of 600.degree.-770.degree. C. and,
more preferably, within the range of 690.degree.-730.degree. C. The omega
zeolite composition next undergoes two final and successive ion exchange
treatments each of which differs from the earlier exchanges in that proton
ions are exchanged under acidic conditions. The introduction of an
oxidizing agent such as nitric acid into the ion exchange medium assists
in creating a solution of an acidic character. The surface area of steamed
omega after the two successive proton ion-exchanges under acidic
conditions increases from about 85 m.sup.2 /g to about 555 m.sup.2 /g.
Additionally, the molar ratio of SiO.sub.2 /Al.sub.2 O.sub.3 of the omega
zeolite increases from about 7:1 to about 38:1. Following the second
proton ion exchange, the omega zeolite composition is mixed with a binder
such as pure alumina in the presence of nitric acid and then pelletized by
any suitable technique such as extrusion. The resulting pellets are then
calcined at a maximum temperature of 530.degree. C. At this point in the
modification, the omega zeolite composition is in its active hydrogen (H)
form and exhibits an ammonium content of less than 0.005 wt. %. The next
treatment of the omega zeolite composition involves its being loaded with
a metallic hydrogenation agent such as any of the Group VIII metals and,
more preferably, nickel. Employing standard techniques, the modified omega
zeolite composition of the present invention is impregnated with a
desirable amount of nickel or other Group VIII metal as a final
modification treatment.
In a comparison study conducted over a period of twenty seven (27) days,
three distinct metal-promoted, modified omega zeolite catalyst
(distinguishable only based upon their weight percentage of nickel) were
utilized in toluene disproportionation reactions yielding benzene and
xylene(s). In this work, an omega zeolite parent compound steamed at
approximately 700.degree. C. was used. Preparation of the steamed omega
composition was performed in accordance with the procedure as earlier
described and as summarized in Table 1.
TABLE 1
__________________________________________________________________________
Summary of omega zeolite modification steps together with comparative
results
of elemental analysis respecting Si/Al molar ratio, surface area and
pore volume for each of the three omega zeolite compositions studied.
Description of
SiO.sub.2 /Al.sub.2 O.sub.3
Surface Area,
Pore Volume,
Step #
Treatment Molar Ratio
m.sup.2 /g
ml/g
__________________________________________________________________________
0 As synthesized with
6.6 83.2 0.0110
template
1 1st ammonium ion-
exchange and calcined
at 570.degree. C.
2 2nd ammonium ion- 69.1 0.0054
exchange
3 3rd ammonium ion- 75.1 N/A
exchange
4 Steamed at 700.degree. C.
7.0 123.2 0.0221
5 1st proton ion-
14.5 430.6 0.1229
exchange under acidic
conditions
6 2nd proton ion-
38.0 555.8 0.1535
exchange under acidic
conditions
7 Extruded with 20% 452.9
alumina binder and
calcined at 530.degree. C.
8 0.33 wt % Ni impregnated
6.9 431.6 0.0992
on extrudate
9 0.62 wt % Ni impregnated
6.6 427.0 0.0977
on extrudate
10 0.75 wt % Ni impregnated
6.6 421.0 0.0959
on extrudate
__________________________________________________________________________
The steamed omega which was subsequently proton ion-exchanged was extruded
with approximately 20% pure alumina binder and was calcined at
approximately 530.degree. C. A dehydrogenating/hydrogenating metal, such
as nickel, was then incorporated into the material in weight percentage
quantities within the range of about 0.3 to 0.8, by utilizing a
conventional impregnation technique with a nickel nitrate
[Ni(NO.sub.3).sub.2 ] solution. At study commencement, an established
volume of the catalyst (i.e. 15 ml.) was loaded into the laboratory
reactor. The reactor was then closed and pressure-tested at 1000 psi prior
to sandbath introduction. Once loaded into the fluidized beds and attached
to the system, the catalyst was dried by heating under hydrogen flow (0.4
L/min.) at 175.degree.-200.degree. C. which condition was maintained
overnight. The reactor temperature was next raised to 250.degree. C. and
held. Pressure was adjusted to and maintained at a value of about 600
psig. The feed containing substantially pure (>99.6%) toluene was then
introduced at a desired rate to provide a LHSV=.about. 2. Hydrogen gas
supplied as cofeed was adjusted to provide a hydrogen-to-toluene feed
ratio of about 3.5:1 to 4.5:1. The reactor temperature was raised in
step-wise increments of about 10.degree.-15.degree. C. until the
conversion of toluene was obtained at a level of 46%-48%. Both liquid and
gas samples were withdrawn during each collection and analyzed to
calculate activity and product selectivity. Toluene conversion within the
defined range was maintained by increasing reactor temperature, which
increase, although small, was required due to catalyst deactivation. As
revealed by Table 2, however, in which the performance of Applicant's most
preferred embodiment is profiled, the rate of catalytic deactivation for
the modified omega catalyst containing about 0.6 weight percent nickel was
measured at a stable 0.6.degree. C./day.
TABLE 2
__________________________________________________________________________
Temperature, conversion and product selectivity of toluene
disproportionation
on Ni(0.62%)/Omega catalyst.
% Product Selectivity
Run day #
Temp/.degree.C.
% Tol Conv
Nonarom
Benzene
Xylenes
Heavies
C1-C5 Gases
__________________________________________________________________________
0.2 246.8 13.63 22.47
24.62
35.50
10.36
0.31
1.0 272.3 35.50 1.22 39.54
50.25
4.68 0.36
2.0 287.8 47.78 1.10 40.47
47.48
7.48 0.58
3.0 286.8 50.07 0.96 40.55
46.55
7.94 0.53
4.0 284.8 49.06 0.83 40.23
47.03
7.47 0.53
5.0 282.5 47.74 0.80 40.68
47.87
7.19 0.46
6.0 282.8 47.57 0.82 41.04
47.55
7.38 0.42
7.0 285.0 48.69 0.85 40.91
47.42
7.83 0.49
8.0 285.8 48.00 0.84 41.19
48.17
7.78 0.46
9.0 287.6 48.55 0.88 42.38
46.34
7.47 0.44
10.0 287.5 48.40 0.81 41.52
46.77
7.50 0.50
11.0 287.5 48.69 0.78 41.14
46.98
7.50 0.50
12.0 288.5 48.78 0.78 41.49
46.40
7.37 0.49
13.0 288.1 47.88 0.70 40.71
47.93
7.48 0.36
14.0 288.5 47.80 0.70 41.64
47.00
7.20 0.40
15.0 290.0 47.57 0.66 40.33
48.26
7.45 0.46
16.0 291.5 47.69 0.66 40.38
47.88
7.44 0.46
17.0 291.5 47.56 0.66 40.73
48.54
7.66 0.39
18.0 292.8 48.22 0.66 41.25
47.59
7.34 0.56
19.0 292.8 47.43 0.66 41.97
46.99
7.21 0.48
20.0 293.2 47.35 0.69 41.97
46.99
7.21 0.48
21.0 295.5 48.08 0.60 41.54
47.13
7.53 0.53
22.0 296.8 48.09 0.62 40.14
47.34
7.63 0.50
23.0 298.6 47.99 0.61 40.28
47.49
7.69 0.54
24.0 299.6 47.89 0.59 40.05
48.04
7.88 0.52
25.0 298.1 47.62 0.61 40.07
47.09
8.24 0.53
26.0 299.5 47.31 0.56 40.16
48.05
7.65 0.51
27.0 300.8 47.69 0.56 40.17
48.08
7.85 0.54
__________________________________________________________________________
Table 3 provides a summary of the most salient performance characteristics
respecting each of the three catalysts studied and includes a
corresponding start of run temperature for each which is defined as the
temperature at which the catalyst gives 46-48% alkylaromatic conversion at
zero time on stream.
TABLE 3
__________________________________________________________________________
Corresponding start of run temperatures and product distribution
breakdown for each of the three omega zeolite catalysts studied.
% Product Selectivity
Catalyst SOR/.degree.C.
Benzene
Xylenes
Non-aromatics
Heavies
__________________________________________________________________________
0.33% Ni/Omega
293 40 47 0.5 7.5
0.62% Ni/Omega
280 40 47 0.5 7.5
0.75% Ni/Omega
289 40 47 0.5 7.5
__________________________________________________________________________
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